In a friction damper of this kind, known from U.S. patent application Ser. No. 187,186, filed Sept. 15, 1980, now replaced without prejudice by Ser. No. 494,680 filed May 16, 1983 the housing consists of a cylindrical metal tube, while the tappet is in one piece, made of some suitable plastic, such as polyamide. This friction damper has proved itself to be of extraordinarily great utility, primarily in washing machines with a spin cycle.
During normal washing operation, washing machines with a spin cycle are driven at a subcritical rotational speed of the vibrating system of the washing machine. During spinning, the drum of the machine is driven at a supercritical rotational speed; that is, as the machine accelerates up to spinning rpm, the vibrating system passes through the critical rpm level. The wet laundry that is located in the drum after the wash cycle and before the spin cycle represents a considerable eccentricity, resulting in considerable imbalancing forces upon acceleration into the spin cycle speed. During this acceleration, the damper must accordingly effect powerful damping. Since the imbalance decreases sharply as the water is spun out of the drum, and because in any event the vibration amplitudes of the vibrating system decrease sharply in the supercritical rpm range, only limited damping force must be produced once the machine has passed back through the critical rpm level. Hydraulic dampers for this purpose are already known, which enable reducing the hydraulic damping forces toward the end of the spin cycle.